Seminar "Theory of Hadronic Matter under Extreme Conditions"

Forthcoming talks

Past talks

05.12.2018 Natalia Kolomoyets, Vladimir Skalozub (Dnipro National University, Ukraine)
"Screening mass of gluons in presence of external Abelian chromomagnetic field" pdf
Abstract:
Screening mass is the main macroscopic characteristic of a gauge field at finite
temperature. It shows how fast the gauge field decreases in space.
There are electric and magnetic screening masses. It is known that in SU(N) gauge
theory the former one is proportional to $gT$, while the second
one is proportional to $g^2T$. So, at high temperature the magnetic mass is much
less than electric one, and is harder to investigate.
In the current research the contribution of various color components of
chromomagnetic field into the magnetic mass is investigated by methods of
lattice gluodynamics at finite temperature. The interaction between a
monopole-antimonopole string and external neutral Abelian chromomagnetic field is
considered. The string is introduced in the standard way described by Srednicki and
Susskind. The neutral Abelian field is introduced in the form of a
flux through the twisted boundary conditions. Monte Carlo simulations are performed
on 4D lattices. The derivative of the free energy with respect to
the inverce coupling is the measured quantity.
In SU(2) case in the absence of the external Abelian flux, the result by DeGrand and
Toussaint is reproduced. We have obtained that the flux
addition weakens the screening of the string field. The contribution of the neutral
Abelian flux to the measured quantity has the enhancing factor form.
This behavior independently confirms the long-range nature of the neutral Abelian
field reported in the literature.
In SU(3) case even without the additional Abelian flux the absence of screening of
the monopole-antimonopole string has been obtained.
This result is unexpected and is discussed within the context of the results of
other investigations.

04.12.2018 Dragos-Victor Anghel (Horia Hulubei National Institute of Physics and Nuclear Engineering, Romania)
"Physics at the meso-scale: toroidal moments and non-extensive entropies" pptx
Abstract:
1. Statistical processes of mesoscopic systems (e.g. nano-, nuclear, and astronomic systems) cannot be described, in general, by the Boltzmann-Gibbs entropy (mainly) because they are not extensive. In such cases, other types of entropies—the so called non-extensive entropies—seem to be better suited for the task. There are different techniques for calculating the equilibrium probability distributions of non-extensive systems, techniques which may not lead to the same results. The justification of these techniques come, eventually, a-posteriori, by comparing the calculated distributions with the ones measured or inferred from the experiment.
In this presentation we propose a general approach for calculating the equilibrium probability distributions, applicable to both, extensive and non-extensive systems, and to any expression of the entropy. We exemplify the procedure by applying it to Boltzmann-Gibbs, Renyi, Tsallis, and Landsberg-Vedral entropies and discuss the results (D. V. Anghel and A. S. Parvan, J. Phys. A: Math Theor. 51, 446002, 2018).
2. Although the multipole decomposition of charge and current densities is almost as old as classical electrodynamics, a whole class of terms has remained unknown for a long time. The history of toroidal moments began with Zeldovich's pioneering work (Zh. Exp. Teor. Fiz. 33, 1531, 1957; Sov. Phys. JETP 6, 1184, 1958). He was the first to note that a closed toroidal current (which cannot be reduced to a usual charge or magnetic multipole moment) represents a certain new kind of dipole.
The necessity for studying the toroidal momentum operator is justified by its large area of applicability in physics at any scale (subnuclear, nuclear, atomic, molecular and condensed matter physics). There is a whole class of particles--the Majorana fermions and self-conjugate bosons--which are not allowed to possess any electromagnetic structure other than toroidal multipole moments and this comes from CPT invariance alone. Meanwhile, the most important facts we need to know about an operator are its spectrum and its eigenfunctions. Consequently, in this presentation we shall solve this problem. In order to do this, we introduce the toroidal momentum operator and study some of its properties. We propose a new set of coordinates in which the operator becomes a simple derivative along one of the coordinates. This enables us to find the eigenvalues and the eigenfunctions (D. V. Anghel, J. Phys. A: Math. Gen. 30, 3515, 1997).

31.10.2018 Roman Zhokhov (IHEP, Protvino), Tamaz Khunjua (Moscow State University)
"Phase diagram and dualities of dense baryonic matter with chiral
imbalance" pdf, pdf
Abstract:
In this talk the phase structure of the dense quark matter has been investigated in the presence
of baryon ​ μ​_B​ , isospin ​ μ​_I​ , chiral ​ μ​_5 ​and chiral isospin ​ μ​_I5 ​chemical potentials in the framework of
Nambu--Jona-Lasinio model with two quark flavors. It has been shown that in the large-​N​_c ​limit
(​ N​_c​ is the number of colors of quarks) there exist duality correspondences at the phase portrait.
The first one is a duality between the chiral symmetry breaking and the charged pion
condensation phenomena. And there are two other dualities that hold only for chiral symmetry
breaking and charged pion condensation phenomena separately. For example, we have shown
that charged pion condensation does not feel the difference between chiral and isospin
imbalances of the medium. The duality between the chiral symmetry breaking and the charged
pion condensation phases has been established for the first time in low-dimensional toy model
for QCD then it has been checked to take place in a more realistic effective model for QCD. One
of the key conclusions of our studies is the fact that chiral imbalance generates charged pion
condensation in dense baryonic/quark matter. It was also shown that our results in particular
cases are consistent with the simulation of lattice QCD, which is possible for isospin and chiral
chemical potentials. Moreover, in a number of works, catalysis of chiral symmetry breaking by
chiral imbalance was predicted, but there were also works that predict the opposite effect. After
lattice calculations that confirmed the effect of catalysis of chiral symmetry breaking, we can, of
course, say that the problem has been solved, but it would be interesting to find out the reasons
for the discrepancy between the results of effective models. We have made a small step in this
direction and showed that, based on the dualities and the well-studied properties of the phase
structure of QCD with only isotopic imbalance, one can conclude that there should be an effect of
catalysis of chiral symmetry breaking. It was also shown that the fact that the chiral imbalance
generates the phenomenon of charged pion condensation in dense baryonic/quark matter also
remains true for the case of charge neutral matter, which is interesting in the context of the
astrophysics of neutron stars. It is known that chiral imbalance can occur in high energy
experiments on the collision of heavy ions, due to temperature and sphaleron transitions. Our
studies show that different types of chiral imbalance can occur in the cores of neutron stars or in
heavy ion experiments where large baryon densities can be reached, due to another
phenomenon - the so-called chiral separation effect (although there were references to this
possibility, we explored it in more details).

25.10.2018 Tobias Fischer (Institute of Theoretical Phyiscs, University of Wroclaw, Poland)
"Explosions of massive blue-supergiant stars triggered by the QCD
phase transition " pdf
Abstract:
Motivated from the observations of yet-unexplained explosive phenomena associated with
massive blue-supergiant stars with zero-age main sequence (ZAMS) masses around 50 M_o, new light has been shed on the old idea [1] that the appearance of QCD degrees of freedom may explain such cosmic events [2]. Obeying chiral physics and taking yet-another important observation of the very existence of massive neutron stars of 2 M_o seriously into account, puts
sever constraints on the behavior of the equation of state at supersaturation density (\rho_{sat}). In particular, sufficient stiffness with increasing density is required. Both aspects indicate rather
high densities for the hadron-quark phase transition in excess of 2\rho_{sat} (at zero temperature).
As a consequence, this excludes low- and intermediate mass stars (~ 10 − 15 M_o ) -- they are canonically considered in supernova studies -- from the presence of ’exotic’ high-density phases. On the other hand, during the evolution of very massive core-collapse supernova
progenitors with ZAMS masses of about 50 M_o , significantly higher core temperatures and densities are reached, where the appearance of the hadron-quark phase transition triggers not only the supernova explosion onset but also a millisecond neutrino burst is released. The latter observable signal provides evidence not only for the presence of a 1st-order phase transition at supersaturation density but contains also details about its properties. The future observation of such a feature from the next galactic event will allow us to either confirm such scenario or, if not observed, rule out a (strong) 1st-order phase transition at high densities encountered in astrophysics. In this talk I will review this scenario in the light of presently known constraints from nuclear physics as well as observations. The latter includes the first binary neutron star merger event associated with GW170817 [3]. Furthermore, I will discuss implications for astrophysics, e.g., the remnants from such supernova explosions are massive neutron stars with
quark-matter core of 2 M_o at birth.
Keywords: core-collapse supernovae --- equation of state --- quark matter
References:
[1] I. Sagert, T. Fischer, M. Hempel, G. Pagliara, J. Schaffner-Bielich, et al., ``Signals of the
QCD phase transition in core-collapse supernovae,'' Phys.Rev.Lett., 102, 081101 (2009).
[2] T. Fischer, N.-U. F. Bastian, M.-R. Wu, P. Baklanov, E. Sorokina, S. Blinnikov, S. Typel,
T. Kl¨ahn, and D. B. Blaschke, ``Quark deconfinement as supernova explosion engine
for massive blue-supergiant stars,'' Nature Astronomy (in press), ArXiv e-prints astroph.HE/1712.08788 (2017).
[3] B. P. Abbot, \textit{et al.} [LIGO scientific and Virgo collaborations] ``GW170817: ``Observation of Gravitational Waves from a Binary Neutron Star Inspiral'', Phys.Rev.Lett., 119, 161101 (2017)

26.09.2018 Giuseppe Policastro (Ecole Normale Superieure, Paris)
"On some solvable non-conformal holographic models for QCD " pdf
Abstract:
In recent years the holographic correspondence has been shown to be a very useful
tool to get theoretical insight into strongly coupled systems such as the QCD quark/gluon
plasma and strongly correlated electrons among others. I will present a class of holographic
models that are useful toy models, because they can be studied analytically while
having features resembling the real QCD, in particular for the running of the coupling. I
will discuss the black hole solutions in these models that are dual to the plasma, and their
unusual thermodynamic and transport properties as seen in the collective modes
spectrum.

03.09.2018 David Fuseau (SUBATECH, Nantes)
"Equation of state at finite temperature
and finite chemical potential using PNJL model
" pdf
Abstract:
We present an equation of state at finite temperature and finite chemical potential
using the PNJL model. The equation of state goes to the next to leading order O(1/N_c) including mesons contributing to the pressure of the medium below T_c. Together
with a new parametrisation of the effective Polyakov loop involving the presence of
quarks in the determination of the critical temperature, we determine pressure
at zero chemical potential matching the result of the lattice and expand to finite
chemical potential. Also derivatives such as the entropy density, energy density, measured
interaction and speed of sound are very similar to lattice results at zero chemical
potential and can be expanded to finite chemical potential. Regarding the finite
chemical potential, the Taylor expansion around zero chemical potential also matches
the results of the lattice. Main applications could be neutron star calculations and
input for transport hadronisation.

09.07.2018 Trambak Bhattacharyya (BLTP JINR & University of Cape Town)
"Non-extensive Statistics in High Energy Physics" pdf
Abstract:
We shall discuss the basics of the Tsallis Non-extensive distribution and
afterwards, we discuss the analytical calculations of the Tsallis
thermodynamic quantities and applications
of the Tsallis statistics in multi-particle production and in
characterizing the hot and dense medium (Quark Gluon Plasma) created in
high energy collisions.

04.07.2018 S. Khlebtsov, Y. Klopot (BLTP JINR), A. Oganesian, O. Teryaev
"Dispersive approach to non-Abelian axial anomaly and $\eta$, $\eta'$ production in heavy ion collisions." pdf
Abstract:
We sudy manifestations of strong and electromagnetic axial anomalies in two-photon decays of $\eta$ and $\eta'$ mesons. Applying dispersive approach to axial anomaly in the singlet current, we obtain an anomaly sum rule containing strong and electromagnetic anomaly contributions. The relevant low energy theorem was generalized to the case of mixed states and used to evaluate the subtraction constant of the strong anomaly-related form factor. We made a numerical estimation of the contributions of gluon and electromagnetic anomalies to the two-photon decays of $\eta$ and $\eta'$ mesons and found significant suppression of the gluon anomaly contribution.
We duiscuss the rate of direct production of $\eta$ and $\eta'$ mesons in heavy ion collisions.

04.04.2018 G. Prokhorov (BLTP JINR), O. Teryaev
"Anomalous axial current from covariant Wigner function and thermodynamic
equilibrium density operator" pdf
Abstract: We considered a rotating and accelerated moving medium consisting of
weakly interacting fermions in a state of local thermodynamic equilibrium
based on two different approaches. In the first of the approaches, the
properties of such a medium are described using the covariant Wigner
function. We derived a formula for the axial current outside the
perturbation theory, leading to a Chiral vortical effect in the limiting
case. It is shown that in the limit of massless fermions the terms of
higher orders in the thermal vorticity tensor are mutually compensated.
In order to verify the results obtained, a second approach to the
calculation of the axial current was used, based on the quantum density
functional for a medium with rotation and acceleration. Carrying out the
calculation of thermodynamic averages in the framework of quantum field
theory at finite temperatures in the third order of perturbation theory,
we obtained the mean values ​​of the axial and vector currents. A
generalization is made to the case of a nonzero axial chemical potential.
The results obtained with the help of the Wigner function and the density
operator are compared with each other and with the consequences of other
approaches, such as effective field theory with axial anomalies. Based on
the obtained formulas for the axial current, the correspondence of various
approaches to the calculation of polarization of baryons is justified.

07.03.2018 Ya. Shnir (BLTP)
"Rational maps, crystals and multisolitons in the Skyrme model" pdf
Abstract: Relation between Yang-Mills theory and Skyrme model is discussed.
We consider rational map approach and the structure of multisoliton
solutions of the Skyrme model and the Faddeev-Skyrme model. The properties
of triply periodic Skyrme crystals in the generalized Skyrme model are
investigated. Various scenarios of phase transitions from the low-density
phase to the high-density phase are examined for different choices of the
parameters of the model. Considering the near-Bogomolny-Prasad-Sommerfeld
submodel, we found that there are indications of the phase transition from
a low-density quasi-liquid phase to the high-density symmetric phase of
the Skyrmionic matter.

27.02.2018 Andrey Kotov (BLTP JINR & ITEP NRS KI)
"Study of properties of two color QCD at nonzero baryon density by means of
lattice simulation" pdf
Abstract: Vacuum and finite temperature properties of QCD are well studied due to the
method of
lattice simulations. Unfortunately, in general case lattice simulations cannot
be applied
for QCD at nonzero baryon density due to the sign problem.
In this report we present the results of lattice simulation of the theory
which is free from the sign problem - two color(SU(2)) QCD at nonzero baryon
density.
Both SU(3) and SU(2) theories have many common phenomena and properties and
study
of SU(2) QCD can provide some information about the properties of real QCD.
Calculations were carried out at zero temperature and with two flavors of
dynamic quarks.
In our study we found several phases of dense two color QCD:
the hadronic phase at small chemical potential (\mu_q); the phase
of Bose-Einstein condensation of scalar diquarks at intermediate
values of \mu_q; the phase with condensation of quark Cooper pairs
at large \mu_q.
At ultrahigh densities (\mu_q~1000 MeV) we found confinement/deconfinement
transition which manifests itself
in rising of the Polyakov loop and vanishing of the string tension.
Properties of the deconfinement phase at large densities are similar to weakly
interacting
gas of quarks and gluons, contrary to Quark-Gluon Plasma at large temperatures
and zero baryon density.

14.02.2018 Felix Ziegler (Institute for Theoretical Physics, Heidelberg University)
"Novel lattice simulations for transport
coefficients in gauge theories" pdf
Abstract: Transport coefficients, such as the temperature-dependent shear and bulk
viscosities, are essential QCD ingredients in the hydrodynamical
description of relativistic heavy-ion collisions. The extraction of the
transport coefficients from lattice simulations is extremely challenging since
a reliable spectral reconstruction from Euclidean data at low frequencies is
required. In standard simulations at finite temperature this reconstruction
is based on the discrete Matsubara frequencies, and is
exponentially hard: the thermal part of the low frequency information is
hidden in the thermal decay of the Euclidean data at large frequencies.
In order to overcome this limitation, we apply the novel approach for
thermal fields on the lattice [1] to gauge fields [2]. The formalism
operates in a non-compact imaginary time domain that leads to continuous
imaginary time frequencies. The quantum evolution is formulated as an
initial value problem and the thermal initial conditions are supplied by a
standard lattice simulation.
We present results for the energy momentum tensor correlation function in
SU(2) Yang-Mills theory in the confined and deconfined phase. Convergence
properties to the standard results at finite Matsubara frequencies are
discussed. Moreover we show first results for the corresponding spectral
functions obtained via the Bayesian BR method [3]. We assess the viability
of the method applied to gauge fields and its ability to provide a robust
estimate for transport coefficients.
[1] J.M. Pawlowski, A. Rothkopf, arXiv:1610.09531 [hep-lat]
[2] J.M. Pawlowski, A. Rothkopf and F. Ziegler (in progress)
[3] Y.Burnier, A.Rothkopf, PRL 111, 182003 (2013)

06.12.2017 V.V. Goloviznin, A.M. Snigirev (SINP MSU & BLTP JINR), G.M. Zinovjev.
"Anisotropy of thermal photons and dileptons" pdf
Abstract: Search for the signals of a new state of matter, quark-gluon plasma (QGP),
is one of the main goals of experiments on heavy-ion collisions at high
energies at modern colliders RHIC and LHC and at coming soon facilities
FAIR and NICA. In this talk the meaningful specific anisotropy in the
angle distribution of leptons with respect to the three-momentum of pair
is predicted as a feasibility signature of synchrotron-like mechanism
resulting from the quarks interacting with a collective confining color
field in the heavy ion collisions. The photon and lepton pair production
rate and the spectrum of pair invariant mass are presented for this new
dilepton source that is apparently not taken into consideration in the
available phenomenological estimates.

25.10.2017 Maksim Ulybyshev (Regensburg U.)
"Topologically protected states in 2D and 3D: spin-momentum and
valley-momentum locking mechanisms." pdf
Abstract: Topological insulator is a special state of matter which has a gap in
the bulk, but hosts gapless surface modes protected by non-tirivial
topological invariant.
Spin-momentum and valley-momentum locking mechanisms (the former one
caused by strong spin-orbital coupling) are the underlying physical
reasons for the appearance of the non-trivial topology of the surface
modes. Topological protection suppresses the backscattering for
electronic states on the surface thus leading to promising potential
applications in "dissipationless" electronic and spintronic devices.
We will review the basic concepts in the field and the most prominent
lattice models hosting the topologically protected modes. Namely, we
will describe the Kane-Mele model on hexagonal lattice in two dimensions
and some lattice models on square and diamond lattices in three
dimensions. We will also describe the possibilities for artificial
engineering of topological insulators with both spin- and
valley-momentum locking mechanisms using the deposition of adatoms in
top of graphene sheet.
The stability of topological insulator against the effects of disorder
and electron-electron interaction will be discussed.
Some connections to Lattice QCD will be also reviewed. For instance, the
prominent Wilson fermions in some region of parameters mimic the
presence of spin-orbital coupling and can be used as a model for 3D
topological insulator.

18.10.2017 E.-M. Ilgenfritz (BLTP JINR) (with J.M. Pawlowski, A. Rothkopf (Heidelberg) and A.M. Trunin)
"Transversal and longitudinal gluon spectral functions
across the phase transition
from twisted mass lattice QCD with N_f=2+1+1 flavors" pdf
Abstract: I report on the first application of a novel, generalized
Bayesian reconstruction (BR) method for spectral functions
to the characterization of QCD constituents. These spectral
functions find
applications in off-shell kinetics of the quark-gluon plasma
and in calculations of transport coefficients. The new BR method
is applied to Euclidean propagator data, obtained in Landau
gauge on lattices with $N_f=2+1+1$ dynamical flavors by the
``twisted mass at finite temperature'' (tmfT) collaboration.
The deployed reconstruction method is designed for
spectral functions that can exhibit positivity violation
(opposed to that of hadronic bound states). The transversal
and longitudinal gluon spectral
functions show a robust structure composed of quasiparticle
peak and a negative trough. Characteristic differences between
the hadronic and the plasma phase and between the two channels
become visible. We obtain the temperature dependence of the
transversal and longitudinal gluon masses.

30.11.2016 Victor Braguta (IHEP, Protvino & ITEP, Moscow & Far Eastern Natl. U., Vladivostok & MIPT, Moscow)
"Study of temperature dependence of QCD viscosity"pdf
Abstract: We have studied the QCD viscosity in the vicinity of confinement/deconfinement transition in lattice simulations. In particular, we have computed with high accuracy the correlators of energy-momentum tensor in gluodynamics in the temperature range T/Tc=(0.9, 1.5). Using these correlation functions, we evaluated the spectral densty. Using it, we finally calculated the viscosity. The results of the calculation are in agreement with the values of viscosity, obtained in the RHIC experiment.

23.11.2016 S.P. Khlebtsov (ITEP, Moscow)
"Analysis of the e+e- ->pi^0 gamma process using anomaly
sum rules approach "pdf
Abstract:The process $e+e- -> gamma* -> pi^0 gamma$ was considered using time-like pion transition form
factor, obtained in the approach of the Anomaly Sum Rules(ASR). The
total cross section and angular distribution of the process were
calculated. As the result of the comparison with the data it was
shown that ASR approach provides their good description in the
regions far from the pole. Also there was proposed a method allowing
to give reasonable description of data in the region of pole within
the ASR approach. The strong restrictions for the parameters of the
modified ASR approach were obtained.

17.08.2016 Ernst-Michael Ilgenfritz (BLTP JINR)
"How can lattice QCD describe non-zero baryonic density? Continuation."pdf
Abstract:
The region of large baryonic density is terra incognita in the QCD
phase diagram, at least for ab initio theoretical investigations
usually offered by lattice QCD.
Quenched lattice studies are obviously misleading, and this is known for
20 years when lattice studies with dynamical fermions were turning to the
phase structure of QCD. Dynamical studies are possible, however only with
decreasing reliability, over a region of limited chemical potential. They
give knowledge with controllable precision up to $\mu/T \approx 1$, in
other words, they are practically impossible for cold dense matter and
matter becoming accessible in heavy ion collisions in the energy range
with $\sqrt{s_{NN}}$ between 4 and 10 GeV (so far explored only in the BES
extension program at RHIC down to 7.7 GeV). The region of medium
temperatures and $\mu/T >> 1$ and $\mu_B=3 \mu_q \sim 0.8$ GeV (according
to Cleymans et al. 2006) will become the object of much more dedicated
interest in heavy ion collisions planned at facilities like NICA (MPD) and
FAIR (CBM). This can be considered as their brand mark.
In relatively simple terms, I will give an explanation for the unpleasant
situation in lattice theory, which has its roots in the complex phase
problem (a.k.a. "sign problem"), which has prevented a broad activity and
rapid growth of knowledge (as we were to used to get it for zero baryonic
density with $\mu=0$) over the last 10 years.
An intensive search for possibilities to overcome this "technical barrier"
has attracted human and machine resources to these methodical questions
(detracted away from "number crunching"). This initiative is bearing fruit
now and has revealed a number of promising potential escapes. They are all
related either to "dualization" (choosing a conjugated configuration space
for simulations) or "complexification" (choosing a slightly extended
configuration space).
The conference "Lattice 2016" was dominated in a remarkable manner by this
development.

10.08.2016 Ernst-Michael Ilgenfritz (BLTP JINR)
"How can lattice QCD describe non-zero baryonic density?"pdf
Abstract:
The region of large baryonic density is terra incognita in the QCD
phase diagram, at least for ab initio theoretical investigations
usually offered by lattice QCD.
Quenched lattice studies are obviously misleading, and this is known for
20 years when lattice studies with dynamical fermions were turning to the
phase structure of QCD. Dynamical studies are possible, however only with
decreasing reliability, over a region of limited chemical potential. They
give knowledge with controllable precision up to $\mu/T \approx 1$, in
other words, they are practically impossible for cold dense matter and
matter becoming accessible in heavy ion collisions in the energy range
with $\sqrt{s_{NN}}$ between 4 and 10 GeV (so far explored only in the BES
extension program at RHIC down to 7.7 GeV). The region of medium
temperatures and $\mu/T >> 1$ and $\mu_B=3 \mu_q \sim 0.8$ GeV (according
to Cleymans et al. 2006) will become the object of much more dedicated
interest in heavy ion collisions planned at facilities like NICA (MPD) and
FAIR (CBM). This can be considered as their brand mark.
In relatively simple terms, I will give an explanation for the unpleasant
situation in lattice theory, which has its roots in the complex phase
problem (a.k.a. "sign problem"), which has prevented a broad activity and
rapid growth of knowledge (as we were to used to get it for zero baryonic
density with $\mu=0$) over the last 10 years.
An intensive search for possibilities to overcome this "technical barrier"
has attracted human and machine resources to these methodical questions
(detracted away from "number crunching"). This initiative is bearing fruit
now and has revealed a number of promising potential escapes. They are all
related either to "dualization" (choosing a conjugated configuration space
for simulations) or "complexification" (choosing a slightly extended
configuration space).
The conference "Lattice 2016" was dominated in a remarkable manner by this
development.

7.07.2016 E.E. Kolomeitsev (Matej Bel University, Slovakia)
"Constraints on the nuclear equation of state. Hyperon puzzle of neutron stars"pdf
Abstract:
Measurements of neutron stars with masses larger or about 2 solar masses
imply that the nuclear equation of state (EoS) should be sufficiently
stiff. The stiffness of the Eos is however restricted from above by the
constraint from the analysis of particle flow in heavy-ion collisions.
The dilemma sharpens if hyperons are included. Since Lambdas and Xi
baryons experience attractive potentials in nuclear matter at the
saturation density, a naive extrapolation of these potentials would lead
unavoidably to the appearance of hyperons in neutron star interiors.
That would soften the EoS and lead to the contradiction with the
observable star masses (so-called hyperon puzzle). We show that this
problem can be resolved if one takes into account a reduction of the
mass of the phi meson which mediates a repulsion among hyperons. We
propose a relativistic mean-field model with hadron masses and coupling
constants depending on the scalar field. All hadron masses undergo a
universal scaling, whereas the coupling constants are scaled
differently. The appearance of hyperons in dense neutron star interiors
is accounted for. The equation of state satisfies well the constraints
known from analyses of the astrophysical data and particle production in
heavy-ion collisions.

16.06.2016 Anastasia Golubtsova (BLTP JINR)
"Evolution of holographic Wilson loops in anisotropic quark-gluon
plasma"pdf
Abstract:
In this talk we discuss the evolution of Wilson loops
in anisotropic quark-gluon plasma using the holographic approach.
We evaluate the Wilson loops in both static and time-dependent cases.
The anisotropic time-dependent plasma is dual to Lifshitz-Vaidya
background, while we use a black brane in the Lifshitz-like spacetime
for a finite temperature plasma in equillibrium.
To probe the system we calculate Wilson loops oriented in different
spatial directions. We find that anisotropic effects in the Lifshitz-like
backgrounds are more visible for the Wilson loops lying in the
transversal direction unlike the Wilson loops partially oriented in
the longitudinal one.

04.05.2016 Maxim Andreichikov (ITEP, Moscow) "Mass spectra of hadrons in strong magnethic field" pdf
"Массовые спектры адронов в сильном магнитном поле"
Abstract:
Mass spectra of neutral mesons and baryons in a strong magnetic field are considered. The spectra are obtained by means of the vacuum correlators approach and by taking into account confinement and perturbative corrections. The results are compared with the lattice calculations.

20.04.2016 A. Yu. Kotov (ITEP, Moscow) "Study of the influence of external effects on the properties of QCD by means of lattice simulation" pdf "Изучение влияния внешних воздействий на свойства КХД методами решеточного моделирования" (по материалам кандидатской диссертации)
Abstract:
The author of the thesis, A. Yu. Kotov, will present the main results of
his PhD dissertation "Modelling the influence of external effects on the
properties of QCD by means of lattice simulation".
In particular, the following questions will be discussed:
-- lattice calculation of the viscosity of the quark-gluon plasma
including its dependence on temperature
-- first results concerning the properties of two-color QCD with
non-vanishing baryon density
-- study of the phase diagram of QCD with non-vanishing chirality imbalance
-- lattice study of an exotic superconducting phase of QCD under the
influence of very strong magnetic fields.

19.04.2016 Atsushi Nakamura (Far East Fed. Univ., Vladivostok, Russia; Hiroshima Univ., Japan; RCNP, Osaka Univ., Japan; Nishina Center, RIKEN,
Wako/Saitama, Japan) "Study of QCD Phase Diagram by Heavy Ion Experiments and Lattice QCD
Experiments"pdf
Abstract:
To explore the QCD phase structure, we must study QCD at finite
temperature and density. A first-principle calculation, lattice QCD, is
expected to provide essential information, but it suffers from the
so-called the sign problem. The fundamental tool of lattice QCD is Monte
Carlo simulation of a path integral, but the measure is
complex at finite chemical potential.
In order to avoid this problem, I propose a canonical approach, in which
the grand partition function, $Z(\mu,T)$, is expanded as a
polynomial of the fugacity, $\xi=\exp(\mu/T)$, where $\mu$ and $T$ are
chemical potential and temperature, respectively:
$Z(\mu,T) = \sum_n Z_n(T) \xi^n$, and $Z_n(T)$ are the canonical
partition functions.
Canonical partition functions are related to the net baryon
distribution, which are measured in high energy nuclear reactions,
although the experimentally measured quantity is the net-proton
distribution. Nevertheless, the net-proton multiplicity may be a
proxy of the net baryon distribution.
Other observables, such as the net-charge fluctuation and the
net-strangeness fluctuation, can be measured both in nuclear and
lattice experiments.

11.04.2016D. Ebert (Humboldt Universit\"at Berlin), T.G. Khunjua (Moscow State University), K.G. Klimenko (IHEP, Protvino), V.C. Zhukovsky (Moscow State University) "Competition and duality correspondence between chiral and superconducting
channels in (2+1)-dimensional four-fermion models "pdf
Abstract:
I will explain the duality correspondence between
fermion-antifermion and di-fermion interaction channels
as established in two (2+1)-dimensional Gross-Neveu
type models with a fermion number chemical potential
μ and a chiral chemical potential μ_5.
The role and influence of this property on the phase
structure of the models are investigated. In particular,
it is shown that the chemical potential μ_5 promotes
the appearance of dynamical chiral symmetry breaking,
whereas the chemical potential μ contributes to the
emergence of superconductivity.
arXiv:1603.00357

24.02.2016 D. Blaschke (Wroclaw University, Poland & BLTP JINR), N.-U. Bastian (Wroclaw University, Poland) "Three-fluid hydro based event simulation for the NICA energy scan
and a new EoS with first-order phase transition"pdf (D. Blaschke), pdf (N.-U. Bastian)
Abstract:
In the first part of the seminar we present first results of simulating the
NICA energy scan (\sqrt{s_{NN}}=4-11 GeV) with a new event generator that
is based on a three-fluid hydrodynamics description of the early stage of
the collision, followed by a particlization at the chemical freezeout to
join a UrQMD "afterburner" accounting for hadronic final state
interactions.
We address the directed flow of protons and pions as well as the proton
rapidity distribution for two model equations of state (EoS), with and
without a first order phase transition.
In the second part we present a recently developed hybrid EoS that fulfills
the constraints from compact star phenomenology and describe its advantages
over the
one used in the simulation up to now.

28.09.2015 E.-M. Ilgenfritz (JINR BLTP), V.K. Mitrjushkin (JINR BLTP), I.L. Bogolubsky (JINR LIT), M. Mueller-Preussker (HU Berlin, Germany), V.G. Bornyakov (IHEP Protvino, ITEP Moscow and FEFU Vladivostok) and A. Sternbeck (FSU Jena, Germany) "Lattice study of gluon and ghost propagators in Landau gauge QCD"
pdf
The talk will be given in connection with the submission of a
cycle of publications of the group of authors to the competition
for the JINR award 2015.
Abstract:
I will give an overview over intentions and guiding ideas underlying
the studies of (gauge dependent) propagators in lattice QCD:
-- confinement criteria formulated in terms of propagators
-- control of assumptions underlying continuum approaches
to non-perturbative QCD like Schwinger-Dyson and FRG
-- providing input to continuum approaches to non-perturbative
QCD in order to overcome limitations of lattice QCD (e.g.
non-vanishing baryonic density)
-- problems and ambiguities preventing a unique fixing of the
requested gauge
-- lessons from earlier JINR-Berlin research in the 90-s in
the field of lattice QED
-- change of the infrared paradigm from the "scaling solution"
to the "decoupling solutions"
-- mapping the non-uniqueness of gauge fixing to the family of
ghost boundary conditions specifying the decoupling solutions.

24.06.2015 David Blaschke (University Wroclaw (Poland) and BLTP JINR
) "Robustness of the Baryon-Stopping Signal for the Onset of
Deconfinement in HIC"
pdf
Abstract:
The impact of the experimental acceptance, i.e. transverse-momentum (p_T)
cut-off and limited rapidity region, on the earlier predicted irregularity
in the excitation function of the baryon stopping is studied. This
irregularity is a consequence of the onset of deconfinement occurring in
the compression stage of a nuclear collision and manifests itself as a
wiggle in the excitation function of the reduced curvature (C_y) of the
net-proton rapidity distribution at midrapidity. It is demonstrated that
the wiggle is a very robust signal of a first-order phase transition that
survives even under conditions of a very limited acceptance. At the same
time the C_y for pure hadronic and crossover transition scenarios become
hardly distinguishable, if the acceptance cuts off too much of the
low-p_T proton
spectrum and/or puts too narrow rapidity window around midrapidity. It is
found that the shape of the net-proton rapidity distribution near
midrapidity depends on the p_T cut-off. This implies that the measurements
should be taken at the same acceptance for all collision energies in order
to reliably conclude on the presence or absence of the irregularity. An
outlook is given to actual perspectives of this study in relation to the
NICA MPD experiment.

04.06.2015 A.V. Sadofyev (ITEP, Moscow (Russia) and CTP, Massachusetts Institute of Technology, Cambridge, MA (USA)) "Chiral drag force"
pdfJoint seminar with "Particle Physics".
Abstract:
We showed that there is an anomalous contribution into the drag force
acting on a heavy quark running through the holographic thermal plasma.
This contribution results in a correlation between the chiral magnetic
effect current and the displacement of heavy quarks in a given event. It is
also possible to use the result for further discussion of non-dissipative
nature of chiral effects.

03.06.2015 Yu. B. Ivanov (NRC "Kurchatov Institute", Moscow) "Relativistic Heavy-Ion Collisions within Alternative Scenarios: Directed
and Elliptic Flow"pdf
Abstract:
Analysis of the directed flow ($v_1$)
and transverse-momentum integrated elliptic flow ($v_2$)
in heavy-ion collisions
is performed in the range of collision energies \sqrt{s_{NN}} = 2.7--39 GeV.
Simulations have been done within a three-fluid model
employing a purely hadronic equation of state (EoS) and two versions of the EoS
with deconfinement transitions:
a first-order phase transition and a smooth crossover transition.
High sensitivity of the proton directed flow to the EoS is found.
The directed flow indicates that the crossover deconfinement transition
takes place in semicentral Au+Au collisions in a wide range of
collision energies 4 < \sqrt{s_{NN}} < 20 GeV.
The crossover EoS is unambiguously preferable for the description of
the most part of experimental data in this energy range.
The obtained results
suggest that the deconfinement EoS's in the quark-gluon sector should be
stiffer at high baryon densities than those used in the calculation.
The latter finding is in agreement with that discussed in astrophysics.
%
Simulations demonstrate low sensitivity of $v_2$ of charged particles
to the EoS. All considered scenarios equally well reproduce
recent STAR data on $v_2$(charged)
for mid-central Au+Au collisions and properly describe its
change of sign at the incident energy decrease below
\sqrt{s_{NN}} = 3.5 GeV.
The predicted integrated elliptic flow of various species exhibits
a stronger dependence on the EoS.
A noticeable sensitivity to the EoS is found for anti-baryons
and, to a lesser extent, for
$K^-$ mesons.
In particular, the $v_2$ excitation functions of anti-baryons
exhibit a non-monotonicity within the deconfinement
scenarios that was predicted by Kolb, Sollfrank and Heinz.
However, low multiplicities of anti-baryons
at \sqrt{s_{NN}}< 10 GeV
result in large fluctuations of their $v_2$ which may wash out this non-monotonicity.

18.03.2015 Anna Radovskaya (Lebedev Institute, RAS, Moscow) "Formation of the equation of state in the early stage of ultrarelativistic heavy-ion collisions"
pdf
Abstract:
We discuss a schematic model describing the evolution of matter
created in ultrarelativistic heavy-ion collisions.
We employ the Keldysh formalism in order to describe the relaxation
of a quantum field from the initial, highly excited state.
For the case of a homogeneous scalar field we show the emergence of
the equation of state explicitly.
We present a complete description of subleading corrections and discuss
analytical expressions for some of them.

11.02.2015 Genis Musulmanbekov (LIT JINR) "On Production and Polarization of Hyperons in Heavy Ion Collisions. Continuation."
Abstract:
We discuss a schematic model describing the evolution of matter
created in ultrarelativistic heavy-ion collisions.
We employ the Keldysh formalism in order to describe the relaxation
of a quantum field from the initial, highly excited state.
For the case of a homogeneous scalar field we show the emergence of
the equation of state explicitly.
We present a complete description of subleading corrections and discuss
analytical expressions for some of them.

28.01.2015 Abdel Nasser Tawfik (MTI University Cairo and Egyptian Center of Theoretical Physics) "Transport Coefficients from SU(3) Polyakov Linear-sigma Model"
pdf
Abstract:
In the mean field approximation, the grand potential of SU(3)
Polyakov linear-$\sigma$ model (PLSM) is analysed for the light and
strange chiral phase-transition, $\sigma_l$ and $\sigma_s$, respectively
and for the deconfinement order parameters $\phi$ and $\phi^*$.
Furthermore, the subtracted condensate $\Delta_{l,s}$ and chiral
order-parameters $M_b\,$ are compared with the lattice QCD calculations.
By using the dynamical quasi-particle model (DQPM), which can be
considered as a system of noninteracting massive quasi-particles, we
have evaluated the decay width and the relaxation time of quarks and
gluons. In framework of LSM and when including Polyakov corrections, the
interaction measure $\Delta/T^4$, the specific heat $c_v$ and speed of
sound squared $c_s^2$ have been determined. Furthermore, the thermal
evolution of the normalized quark number $n_q/T^3$ and the
susceptibilities $\chi_q/T^2$ at different baryon chemical potentials
are confronted with the corresponding Stefan-Boltzmann (SB) limits. The
electric $\sigma_e$ and heat $\kappa$ conductivity and their ratio are
compared with the available lattice QCD calculations. The bulk and shear
viscosities normalized to the thermal entropy $\xi/s$ and $\eta/s$,
respectively, and the ratio of bulk and shear viscosities are evaluated
from PLSM compared with the lattice QCD data. Finally, the ratios $(\xi
/s)/(\sigma_e T)$ and $(\eta /s)/(\sigma_e T)$ are calculated.

21.01.2015 David Blaschke (JINR BLTP and Univ. Wroclaw, Poland) "Quantum flavor kinetics and chemical freeze-out"
pdf
Abstract:
We present current status of a quantum kinetic formulation of the chemical
equilibration process in dense hadronic matter at the hadronization
transition. Delocalization of hadron wave functions at the Mott-Anderson
transition (where their binding energies vanish) lead to a divergence of
scattering lengths and critical enhancement of rearrangement collisions
between hadrons. We exemplify this for different meson-meson scattering
processes from light (pi-pi scattering) to heavy flavors (charmonium
dissociation). On this basis we suggest that chemical freeze-out has to be
correlated with (partial) chiral symmetry restoration.

12.11.2014 Genis Musulmanbekov (LIT JINR) "On Production and Polarization of Hyperons in Heavy Ion Collisions."ppt
Abstract:
A new mechanism is explained for the interpretation of the non-monotonic,
enhanced yield of hyperons and strange mesons (also known as "horn" effect),
that is observed in central heavy ion collisions in the experiment NA49 at
SPS and confirmed by STAR at RHIC.
We argue that the data indicate the transition of the nucleons in the
overlap region of the colliding nuclei with high nuclear density into a
certain hyperon phase. In semicentral heavy ion collisions a strong magnetic
field and very large orbital angular momentum can be created. The polarization
of hyperons becoming possible due to these phenomena is discussed.

03.09.2014 Elena Bratkovskaya (ITP & FIAS, Uni. Frankfurt) "Electromagnetic probes of the QGP."pdf
Abstract:
A review of the latest theoretical results on electromagnetic probes
(direct photons and dileptons) of the QGP in heavy-ion collisions at
ultra-relativistic energies will be presented. While the dilepton
spectra at low invariant mass show in-medium effects like a
collisional broadening of the vector mesons in their spectral
functions, the dilepton yield at high invariant masses (above 1.1 GeV)
is dominated by the QGP contributions for central heavy-ion collisions
at ultra-relativistic energies.
Also we discuss the present status of the photon $v_2$ "puzzle" - one
of the challenging topics related to the large elliptic flow $v_2$ of
the direct photons experimentally observed at RHIC and LHC energies.
It turns out that the photonic $v_2$ is as large as the hadronic
$v_2$, whereas many models predict a very small $v_2$ of photons from
the QGP due to their early emission before the system has developed a
sizeable momentum anisotropy. We investigate the role of hadronic and
partonic sources for the photon spectra as well as the possibility to
subtract the QGP signal from the experimental observables by studying
the centrality dependence of the direct photon yield.

27.08.2014 Igor Mishustin (Frankfurt Institute for Advanced Studies, Goethe University, Frankfurt/Main, Germany and
National Research Center "Kurchatov Institute", Moscow, Russia)
"Non-equilibrium Dynamics of the Chiral/Deconfinement Phase Transition."pdf
Abstract:
Observable signals of possible QCD phase transitions are strongly
influenced by the rapid non-equilibrium dynamics during a heavy-ion
collision. In order to realistically estimate these effects we have
developed a non-equilibrium chiral fluid dynamics model, where the
quark-antiquark fluid is dynamically coupled to the order-parameter
fields. The model takes into account dissipation and fluctuation effects
stemming from the interaction between the fluid and the fields. The actual
calculations are done within the linear sigma model with constituent
quarks, coupled to the Polyakov loop. The dynamical trajectories of the
fluid elements on the T-\mu plane are studied for different types of the
phase transition. The effects of supercooling and reheating are clearly
observed in the case of a first-order phase transition. In this case we
see the formation of domains in net-baryon density due to spinodal
decomposition. They should lead to an enhancement of higher harmonics in
azimuthal distributions of net-baryons. It is also demonstrated that
long-wavelength fluctuations near the critical point show a strong
enhancement only in a quasi-static system, but they are suppressed in the
case of a fast expansion.

09.07.2014 Ernst-Michael Ilgenfritz (VBLHEP & BLTP, JINR Dubna) (tmfT collaboration) "Thermal crossover, propagators and equation of state from
N_f=2 and N_f=2+1+1 flavors dealt within the twisted mass approach."
Abstract:
A relative majority of European lattice simulations of full QCD have got concentrated
on the twisted mass approach to Wilson fermions (Collaboration ETMC) as opposed
to other (staggered, clover improved Wilson, domain wall etc.) fermion
formulations.
The "twisted mass at finite temperature" (tmfT) collaboration is a
small group of authors following this approach for simulations at finite temperature,
in particular using the results of ETMC (at a set of
unphysical pion masses) at zero
temperature as input for calibration. Finite temperature simulations have
been performed in order to explore the nature of the phase transition with
two degenerate light flavors (u and d) in the chiral limit and to find
the temperature of the crossover for the physical pion mass.
As a continuation of previous work of the BLTP-Humboldt University
collaboration on Landau gauge gluon and ghost propagators at T=0,
finite-temperature configurations have been used to study the T
dependence of the electric and magnetic gluon propagators in the vicinity
of the crossover. These results are connected with our earlier corresponding
quenched results near to the phase transition of SU(3) pure gauge theory
via the Dyson-Schwinger approach (Ch. Fischer).
The twisted-mass approach with an additional non-degenerate quark doublet,
tuned to realistic s and d quark masses, will be described. The status
of results concerning the temperature of the crossover for would-be pion
masses between 220 and 400 MeV and the contributions of light and heavy
quarks to the equation of state will be reported.

07.07.2014 Alexander Botvina (INR-RAS, Moscow, Russia, and FIAS, Frankfurt/Main, Germany) "Production of hypernuclei from excited nuclear residues in relativistic
ion collisions: New opportunities for BM@N and MPD@NICA."pdf
Abstract:
Investigation of hypernuclei is a rapidly progressing field of nuclear
physics, since they give opportunities both to improve methods of
traditional nuclear studies and to open new horizons for studying particle
physics and nuclear astrophysics. Within dynamical and statistical
theories we study the main regularities in the production of hypernuclei
emerging from the projectile and target residues in relativistic ion
collisions. This process will allow to study the mechanisms of peripheral
collisions and the properties of hyper-matter of low temperatures,
including hyperon-hyperon interactions at low energies. We demonstrate
that the yields of hypernuclei increase considerably at beam energies
above the energy threshold for Lambda hyperons (~1.6 AGeV), followed by a
saturation for yields of hypernuclei with increasing the beam energy up
to few TeV [1]. These hypernuclei have a broad distribution in masses and
isospin. They can even reach beyond the neutron and proton drip-lines
since they are stable with respect to nucleon emission [2]. Weak decay of
such hypernuclei may lead to formation of normal nuclei beyond the
drip-lines also, thus providing a unique chance for reaching island of
stability on the nuclear chart. The production of specific hypernuclei
depend strongly on the isotopic composition of the projectile, therefore,
it will be possible to obtain exotic hypernuclei that may be difficult to
reach in traditional hypernuclear experiments [1]. We also show new
calculations including DCM, UrQMD, and HSD models with formation of light
hypernuclei of all rapidities and large hyper-residues, which can be
obtained in the fixed-target experiments. The perspectives of hypernuclear
studies involving these novel processes at the present accelerators are
discussed.
[1] A.S. Botvina, K.K. Gudima, and J. Pochodzalla,
Phys. Rev. C88, 054605 (2013).
[2] N. Buyukcizmeci, A.S. Botvina, J. Pochodzalla, and M. Bleicher,
Phys. Rev. C88, 014611 (2013).

28.05.2014 Masayasu Hasegawa (BLTP JINR) "Chiral symmetry and overlap fermions, instantons and monopoles in
lattice QCD".
Abstract:
At the end of the 90-s it became clear that overlap fermions realize
chiral symmetry to a maximal degree permitted by lattice discretization.
This has opened the way to study the relation between chiral and
topological aspects of QCD vacuum structure.
It is known -- to a large extent due to the work of the Kanazawa-DESY-ITEP
collaboration on one hand and of the Pisa group on the other -- that
monopoles play a crucial role in the confinement mechanism through
monopole condensation and dual superconductivity.
Whereas instantons offer a beautiful mechanism for spontaneous breaking of
chiral symmetry, a direct relation to confinement is not obvious.
The purpose of the present study reported in this seminar is to show a
relation between instantons and monopoles by using the overlap fermions as
an analytical tool. One non-trivial problem is to relate them, despite the
different dimensionality of instantons (4-dimensional event-like) and
monopoles (3-dimensional particle-like). The exact relation remained
unclear in spite of many studies. Therefore we try to clarify the relation
with the help of overlap fermions on the lattice.
In this seminar, first I will introduce the overlap fermions briefly.
Second, I will explain how to create an additional monopole to a given
lattice configuration. Third, I will give some results showing that this
construction is consistent. Finally, I will present some new results
clarifying the relation between instantons and monopoles.

14.05.2014 Ludmila Malinina (SINP MSU - JINR) "Femtoscopy of heavy ion and pp collisions at high energies."pdf
Abstract:
The femtoscopic correlations allow one to measure the space-time characteristics of
particle production thanks to the effects of quantum statistics for identical particles and
final state interactions for both identical and non-identical ones. The main features of the
femtoscopy measurements in heavy-ion collisions at SPS and RHIC are i) the value of the
radii almost independent on the beam energy, ii) the increase of the correlation radii with
increasing multiplicity of events and iii) the decrease of the radii with increasing of pair
transverse momentum. These are understood as a manifestation of the strong collective
flow. Such effects were also observed at the LHC with the interferometry volume increased
twice compared with RHIC. The data from Pb-Pb collisions and its comparison with the
dynamical models will be presented. The high multiplicity pp collisions
reach particle densities comparable to the ones measured in peripheral Cu-Cu and Au-
Au collisions at RHIC so it is natural to investigate collective behaviour in pp. The
similarities and differences between pp and heavy-ion data are discussed.

7.05.2014 Hans-Peter Pavel (TU Darmstadt & BLTP JINR Dubna) "Low energy QCD in terms of gauge invariant dynamical variables" pdf
Abstract:
Using a generalized polar decomposition of the gauge fields into
gauge-rotation and gauge-invariant parts,
which Abelianises the Non-Abelian Gauss-law constraints to be implemented,
a Hamiltonian formulation of low energy QCD in terms of gauge invariant
dynamical variables can be achieved.
The exact implementation of the Gauss laws reduces the colored spin-1
gluons and spin-1/2 quarks to unconstrained colorless
spin-0, spin-1, spin-2 and spin-3 glueball fields and colorless
Rarita-Schwinger fields respectively.
The obtained physical Hamiltonian naturally admits a systematic
strong-coupling expansion in powers of $\lambda=g^{-2/3}$,
equivalent to an expansion in the number of spatial derivatives.
The leading-order term corresponds to non-interacting hybrid-glueballs, whose
low-lying spectrum can be calculated with high accuracy by solving the
Schroedinger-equation
of the Dirac-Yang-Mills quantum mechanics of spatially constant fields (at
the moment only for the 2-color case).
The discrete glueball excitation spectrum shows a universal string-like
behaviour with practically all excitation energy
going in to the increase of the strengths of merely two fields, the
"constant Abelian fields" corresponding to the zero-energy
valleys of the chromomagnetic potential. Inclusion of the fermionic
degrees of freedom significantly lowers
the spectrum and allows for the study of the sigma meson.
Higher-order terms in $\lambda$ lead to interactions between the
hybrid-glueballs and can be taken into account systematically
using perturbation theory in $\lambda$, allowing for the study of
IR-renormalisation and Lorentz invariance.
The existence of the generalized polar decomposition used, the position of
the zeros of the corresponding Jacobian
(Gribov horizons), and the ranges of the physical variables can be
investigated by solving a system of algebraic equations.
Its exact solution for the case of one spatial dimension and first
numerical solutions for two and three spatial
dimensions indicate that there is a finite number of solutions separated
by Gribov horizons.

16.04.2014 Iu. A. Karpenko (FIAS, Frankfurt & BITP, Kiev) "Beam energy scan using a viscous hydro+cascade model
"pdf
Abstract:
Following the experimental program at BNL/RHIC, we perform a similar
"energy scan" using 3+1D viscous hydrodynamics coupled to the UrQMD hadron
cascade, and study the collision energy dependence of pion and kaon
rapidity distributions and m_t-spectra, as well as charged hadron elliptic
flow. To this aim the equation of state for finite baryon density from a
Chiral model coupled to the Polyakov loop is employed for hydrodynamic
stage. 3D initial conditions from UrQMD are used to study gradual deviation
from boost-invariant scaling flow. We find that the inclusion of shear
viscosity in the hydrodynamic stage of evolution consistently improves the
description of the data for Pb-Pb collisions at CERN SPS, as well as of the
elliptic flow measurements for Au-Au collisions in the Beam Energy Scan
(BES) program at BNL/RHIC. The suggested value of shear viscosity is
\eta_s>0.2 for \sqrt{s}=6.3...39 GeV.

19.03.2014 I. Ya. Aref'eva (Mathematical Institute, RAS, Moscow) "Holographic description of quark-gluon plasma"ppt
Abstract:
The holographic description of the quark-gluon plasma
permits, in principle, to find the interquark interaction and the meson
spectrum, the thermalization time, the multiplicity of particles
being produced,
as well as the hydrodynamical characteristics of the quark-gluon plasma
produced in heavy-ions collisions.
There are several holographic models providing these physical quantities.
The problem of finding a holographic model that simultaneously gives
reasonable values for all these phenomenological parameters will be discussed.

19.02.2014 B.V. Batyunya (JINR, VBLHEP) "ALICE (A Large Ion Collider Experiment) results from the LHC"pdf
Abstract:
The following results are considered for p-p, p-Pb and Pb-Pb collisions:
-Event multiplicity,
-Particle species ratios and spectra,
-Nuclear modification factor for charged particles and heavy Quarkonia,
-Resonance production,
-Bose-Einstein Correlations (Femtoscopic Correlations),
-Azimuthal anisotropic flow.
I shall compare with other experiments and theoretical predictions.
The results are discussed from the point of view
of collective effects and the generation of Quark-Gluon-Plasma in
Heavy Nuclear Collisions.

29.01.2014 M.V. Altaisky (Space Research Institute RAS) "Perspectives of wavelet bases in simulation of lattice theories"pdf
Abstract:
We consider the perspectives of using orthogonal wavelet expansion with Daubechies wavelets for lattice theories. The discrete wavelet transform have been already applied to simulate the Landau-Ginzburg/Ф4 theory with the assumption that the wavelet coefficients of the order parameter Ф(x) are delta-correlated Gaussian processes in the scale-position space. This reduces the autocorrelation time of simulation, and is not the only merit of wavelet transform. By construction the wavelet transform represents the snapshot of a field at a given scale, and therefore can be used as a tool to study the correlations between fluctuations of different scales. For the same reason the relation of wavelet transform to the renormalization group are considered. We also discuss the prospective of wavelet transform to improve the Metropolis algorithm and the simulated annealing procedure.

22.01.2014 Victor Braguta (IHEP Protvino and ITEP Moscow) "Study of the axial magnetic effect"pdf
Abstract:
An axial magnetic field, which couples to left- and
right-handed fermions with opposite signs, may generate in equilibrium
a dissipationless steady energy flow of fermions in the direction of the
field even, in the presence of interactions. We report on a numerical
observation of this Axial Magnetic Effect in quenched SU(2) lattice gauge
theory. We find that in the deconfinement (plasma) phase the energy flow
grows linearly with the increase of the strength of the axial magnetic
field. In the confinement (hadron) phase the Axial Magnetic Effect is
absent. The temperature dependence of the Axial Magnetic effect is
studied.

15.01.2014 Maxim Ulybyshev (Lomonosov Moscow State University, Institute for theoretical problems of microphysics and ITEP Lattice Group) "Chiral symmetry breaking in graphene: a lattice study of excitonic and antiferromagnetic phase transitions."pdfppt
Abstract:
I'll present a review of lattice simulations of graphene electronic
properties. Graphene is an example of a system with strongly correlated
electrons which can be described in the low-energy limit by an effective
field theory with very large coupling constant. Therefore it can be a
subject of spontaneous symmetry breaking with the appearance of various
fermionic condensates. The simulations of graphene electronic properties
can be divided into two branches:
1) calculations within the framework of graphene effective field theory
(2 flavours of (2+1)-dimensional massless Dirac fermions strongly
interacting with ordinary (3+1)-dimensional electromagnetic field);
2) simulations of the original tight-binding model on a hexagonal lattice.
Each method has its own advantages and disadvantages. The main difference
between them are the appearance of different order parameters that
correspond to antiferromagnetic and excitonic phase transitions,
correspondingly.
I'll give the review of both approaches emphasizing the relations between
them: how the results of calculations in the low-energy effective field
theory can be compared with the results of simulations on the hexagonal
lattice which take into account the "ultraviolet" behaviour of quantum
fields.

18.12.2013 D. B. Blaschke, G. A. Contrera, A. G. Grunfeld "Phase diagrams in nonlocal Polyakov-NJL models constrained by Lattice QCD results."pdf
Abstract:
Based on lattice QCD-adjusted SU_f(2) nonlocal Polyakov-Nambu-Jona-Lasinio
(PNJL) models, we investigate how the location of the critical endpoint in
the
QCD phase diagram depends on the strength of the vector meson coupling,
as well as on the Polyakov-loop (PL) potential and the form factors of the
covariant interaction model model.
These are constrained by lattice QCD data for the quark propagator.
The strength of the vector coupling is adjusted such as to reproduce the
slope
of the pseudocritical temperature for the chiral phase transition at low
chemical
potential extracted recently from lattice QCD simulations.
Our study supports the existence of a critical endpoint in the QCD phase
diagram
albeit the constraint for the vector coupling shifts its location to lower
temperatures
and higher baryochemical potentials than in the case without it.

13.11.2013 R.G. Nazmitdinov (BLTP JINR) "Elements of Random Matrix Theory and chaos-order transition in finite quantum systems. Continuation."ppt
Abstract:
We briefly discuss basic elements of Random Matrix Theory which can be
used for analysis of spectra of many-body systems. Considering different
systems such as atomic nuclei, quantum dots and quantum billiards, we
demonstrate the universality of the Random Matrix approach as a tool to
detect the chaos-order transition in finite Fermi systems. It is shown
that this transition occurs at certain conditions which give rise to
dynamical symmetries in chaotic dynamics of fermions.

06.11.2013Boris V. Martemyanov (ITEP, Moscow)
and E.-M. Ilgenfritz (JINR) and M. Müller-Preussker (HU Berlin)
"Topological structure of gluodynamics
close to the transition temperature studied in the IR
by low modes of the overlap Dirac operator" pdf
Abstract:
Topological objects of SU(3) gluodynamics near the transition
temperature are studied at the infrared scale with the help of zero and
near-zero modes of the overlap Dirac operator.
We construct the UV filtered topological charge density in three versions
by choosing different temporal boundary conditions applied to this operator.
In the reference case of analytical (anti)caloron solutions the zero modes
would be located, correspondingly, on three types of constituent dyons
(antidyons), which can be considered as the elusive ``instanton quarks''.
Clustering of the three topological charge densities marks the positions of
dyons and antidyons which are approximately recognizable in equilibrium
(Monte Carlo) gluonic field configurations. We classify them either as
constituents of nondissociated (anti)calorons or as constituents of
(anti)dyon pairs or as isolated (anti)dyons. The pattern of the Polyakov
loop, as it is found inside these clusters after a small number of overimproved
cooling steps, resembles predictions made for analytical caloron solutions.

30.10.2013 Andrey Kotov (ITEP)
"Non-perturbative study of the viscosity in SU(2) lattice gluodynamics" pdf
Abstract:
A calculation of the viscosity of the gluon plasma has been performed
by lattice simulation of $SU(2)$ gluodynamics on supercomputers.
The calculation focuses on a temperature of $T/T_c=1.2$ .
The evaluation is based on the Kubo-formula relating the viscosity to
the spectral function of the correlation function of the energy-momentum
tensor. Problems of the analytical continuation from Euclidean data to
the real-time spectral function are discussed.

23.10.2013 D.N. Voskresensky (NRNU "MEPhI")
"Neutrino cooling of neutron stars" ppt
Abstract:
It will be argued that neutrino emission from dense hadronic component
in neutron stars is subject of strong modifications due to collective
effects in the nuclear matter. With the most important in-medium
processes incorporated in the cooling code an overall agreement with
available X-ray data including new data on Cassiopea A and data on
neutron star masses can be achieved.

16.10.2013 Elena V. Luschevskaya (ITEP)
"The \rho and A mesons in a strong abelian magnetic field in
SU(2) lattice gauge theory" pdf
Abstract:
The correlators of vector, axial and pseudoscalar
currents have been calculated in the background
of a strong abelian magnetic field in $SU(2)$
gluodynamics simulated with an improved gauge action.
The neutral $\rho$ and $A$ meson masses with
different spin projections to the axis parallel
to the external magnetic field ${\vec B}$ have
been calculated. The masses of the neutral mesons
with zero spin $S = 0$ decrease with increasing
strength of the magnetic field.
The masses of the $\rho$ and $A$ mesons with spin
$S = \pm 1$ increase with the value of $|{\vec B}|$.
The mass extrapolation and renormalization also
were performed on the lattice.

02.10.2013 Andrey Leonidov (Lebedev Institute of Physics, RAS, Moscow)
"Turbulent polarization in QED and QCD plasma" pdf
Abstract:
The possibility of turbulent behavior of dense matter created in
ultrarelativistic heavy ion collisions and its experimental manifestations
has recently drawn coniderable attention. In the talk, after a brief introduction
to possible turbulence-related phenomena in heavy ion collisions, we focus on
recent results on polarization properties of Abelian and non-Abelian
turbulent ultrarelativistic plasma. In particular, we discuss possible
turbulence-related instabilities and turbulent modification of plasmon
properties.

25.09.2013 R.G. Nazmitdinov (BLTP JINR) "Elements of Random Matrix Theory and chaos-order transition in finite quantum systems"
Abstract:
We briefly discuss basic elements of Random Matrix Theory which can be
used for analysis of spectra of many-body systems. Considering different
systems such as atomic nuclei, quantum dots and quantum billiards, we
demonstrate the universality of the Random Matrix approach as a tool to
detect the chaos-order transition in finite Fermi systems. It is shown
that this transition occurs at certain conditions which give rise to
dynamical symmetries in chaotic dynamics of fermions.

07.08.2013 Elena Bratkovskaya (ITP&FIAS, Univ. Frankfurt) "The properties of parton-hadron matter from heavy-ion collisions" pdf
Abstract:
The intriguing problem of modern high energy and heavy-ion physics is to
understand the nature of deconfinement and the phase transition
from hadronic to partonic matter - the Quark-Gluon Plasma (QGP)- which
occurs during heavy-ion collisions at relativistic energies.
The latest experimental findings at high energy heavy-ion collisions
indicate that the QGP shows the properties of a strongly interacting
liquid (sQGP) rather than - as expected initially - a weakly interacting
gas of partons.
From the other hand, at low energy one observes a significant
modification of hadronic properties in dense and hot nuclear environment.
An overview of experimental observables as well as theoretical models
for the dynamical description of strongly interaction parton-hadron
matter in- and out-off equilibrium will be presented, the perspectives
for the
future NICA and BM@N experiments will be discussed.

03.07.2013 Sergei Nedelko (BLTP JINR), Vladimir Voronin (BLTP JINR & Dubna Uni.) "A Domain Wall Network as QCD Vacuum: Confinement, Chiral Symmetry, Hadronization" pdf
Abstract:
An overall task pursued by most of the approaches to QCD vacuum structure
is an identification of the properties of nonperturbative gauge field
configurations able to provide a coherent resolution of the confinement,
the chiral symmetry breaking, the $U_{\rm A}(1)$ anomaly and the strong
CP problems, both in terms of color-charged fields and colorless hadrons.
The central subject of the talk is an ensemble of almost everywhere
homogeneous, Abelian and (anti-)self-dual gluon field configurations.
These configurations are represented by a network of domain wall defects
in an initially homogeneous background. A single domain wall is given by
the sine-Gordon kink configuration for the angle between the chromomagnetic
and chromoelectric components of the gauge field. The kink arises as a
solution of the effective equations of motion within the Ginzburg-Landau
approach to the effective quantum action of QCD. The effective action takes
into account the existence of a non-vanishing gluon condensate
$\langle g^2F^2\rangle$ and the symmetries of QCD. The network of domain
walls is introduced by a combination of multiplicative and additive
superpositions of kinks. The spectrum and eigenmodes of color charged field
fluctuations are calculated for the case of an infinitely thin planar Bloch
domain wall. The character of the spectrum and eigenmodes of field fluctuations
in the presence of the network of domain walls characterizes the QCD vacuum
as the heterophase mixed state. The concept of the confinement-deconfinement
transition in terms of the ensemble of domain wall networks is outlined.
The role of a strong electromagnetic field as a trigger of deconfinement is
discussed.
This ensemble of gluon fields provides a setup for description of the main
nonperturbative features of QCD. The phenomenological results obtained
previously in the context of domain model are reviewed: confinement of
static and dynamical quarks, chiral symmetry realization, the $U_A(1)$
anomaly and the strong CP problem, as well as the mechanism of hadronization.
In particular, with a minimal set of parameters (characteristic for QCD)
the model describes the properties of mesons from qualitatively different
parts of the spectrum: light mesons (including the Regge spectrum), heavy
quarkonia, heavy-light mesons, electromagnetic form factors and decay
constants.

26.06.2013 Yongseok Oh (Kyungpook National University, Korea) "Skyrmions with vector mesons: single Skyrmion and baryonic matter" pdf
Abstract:
The roles of light $\omega$ and $\rho$ vector mesons in the Skyrmion are
investigated in a chiral Lagrangian derived from hidden local symmetry
(HLS) up to ${\cal O}(p^4)$ including the homogeneous Wess-Zumino terms.
We write a general master formula that allows us to determine the
parameters
of the HLS Lagrangian from a class of holographic QCD models valid at the
large-$N_c$ and large-$\lambda$ (`t Hooft constant) limit by integrating out
the infinite towers of vector and axial-vector mesons other than the lowest
$\rho$ and $\omega$ mesons. Within this approach we find that the physical
properties of the Skyrmion as the solitonic description of baryons are
independent of the HLS parameter $a$. Therefore the only parameters of
the model are the pion decay constant and the vector-meson mass.
Once determined in the meson sector, we have a totally parameter-free theory
that allows us to study unequivocally the role of light vector mesons in the
Skyrmion structure. We find that the inclusion of the $\rho$ meson reduces
the soliton mass, which makes the Skyrmion come closer to the
Bogomol`nyi-Prasad-Sommerfield soliton, but the role of the $\omega$ meson
is found to increase the soliton mass. This model is also applied to
investigate baryonic matter as Skyrmion crystals.

03.06.2013 Mridupawan Deka (BLTP JINR) "Meta-stable States in the Quark-Gluon Plasma" pdf
Abstract:
In pure $SU(3)$ gluodynamics, the deconfined phase exists in three degenerate
states which are related to each other via $Z(3)$ rotations.
For QCD with dynamical fermions, the $Z(3)$ symmetry is explicitly broken.
As a consequence, the degeneracy between the three states is lifted, and one
of these states becomes the lowest-lying phase. For asymptotically high
temperatures one expects that the effects of quarks can at most render
the other two phases meta-stable.
In this project (Phys.Rev. D85 (2012) 114505) we have studied the meta-stable
phases at high temperature by means of lattice QCD. We have considered $N_f=2$
and $3$ flavours of dynamical staggered quarks, and have carried out
simulations at various values of the inverse gauge coupling $\beta$ to observe
these states. We have estimated the temperature above which the expected
meta-stability appears.

29.05.2013 A. V. Friesen (BLTP JINR) "Scattering of Quarks on Quarks and Hadrons" pdf"Рассеяние кварка на кварке и адроне"
А. В. Фризен, Ю.Л. Калиновский, В. Д. Тонеев
Abstract:
We discuss the Nambu-Jona-Lasinio model with inclusion of the Polyakov loop
(PNJL model). We discuss in particular the parametrization of the effective
potential in the gluon sector. A number of new parameters for the effective potential is introduced,
which are motivated by an approximation of new lattice data.
Then the thermodynamics of this model is studied in detail.
The application of this model to the description of mesons and quarks
embedded in a hot and dense medium is discussed. In particular, the
elastic scattering of quarks with quarks and antiquarks and - for the
first time -
of quarks with hadrons is studied.
Results of numerical calculations for the total and the differential cross
section of a quark on a quark, on an antiquark and on a pion will be
reported.

22.05.2013 Joseph Manjavidze (VBLHEP JINR) "On S-matrix Interpretation of Thermodynamics"
Abstract:
The aim of the talk is to point out the connection between ordinary
S-matrix theory of the multiple production processes and the real
time finite temperature field theory in the sense of Schwinger-Keldysh.
It is shown that a one-to-one connection occurs if and only if the
event-by-event fluctuations of the mean energy of the produced particles
are Gaussian, i.e. the system is in "equilibrium".
The established connection
(i) defines the thermodynamical parameters of the Schwinger-Keldysh
theory through experimental input data and (ii) defines the range of
applicability of thermodynamical approaches to the description of
multiparticle production processes.

07.05.2013 D. E. Alvarez-Castillo (BLTP JINR) "Symmetry energy in the neutron star equation of state and
astrophysical observations" pdf
Abstract:
A systematic study of the role of the nuclear symmetry energy $E_s(n)$ for
the
description of neutron star (NS) matter is presented.
In a first part, the behavior of $E_s(n)$ at subsaturation densities is
discussed which is relevant for the location of the crust-core transition
inside the star and thus for the crust thickness.
We discuss how observations of glitches for the Vela pulsar constrain the
fraction of the crustal moment of inertia and thus $E_s(n)$ at low densities.
In a second part the conjecture of a
universal symmetry energy contribution
to the NS equation of state (EoS) at supersaturation densities is presented.
Ths result is derived from the finding that for NS matter the
asymmetry contribution to the energy per nucleon (in the parabolic
approximation) has a maximum bound as a function of baryon density which
corresponds to a proton fraction being almost constant and below the value
for the threshold of the Direct Urca (DU) cooling mechanism, i.e., around
$x_{\rm DU}\sim 1/8$.
As we have safe knowledge that the DU process cannot be operative in a large
class of NS, the EoS describing the matter their interior cannot allow proton
fractions exceeding $x_{\rm DU}$.
This implies the universal behaviour of the symmetry energy contribution
which can be exploited for linking the EoS determination by NS observations
with that by heavy-ion collision experiments.

10.04.2013 Petr Kopnin (ITEP) "Holographic models of QCD in the strong coupling region." pdf
Abstract:
We discuss several properties of the strongly coupled QCD in the presence of vacuum condensates and external fields in the framework of holographic AdS/QCD models. We investigate the compatibility of the dual AdS/QCD models with the axial low energy theorems of QCD, demonstrating a method of calculating the spectral density of the Dirac operator in dual models. We also discuss the implications of the holographic models for the QCD dynamics in strong external magnetic fields, such as the chiral magnetic effect, the behavior of the Debye screening mass in quark-gluon plasma in the magnetic field, and the dependence of the magnetic susceptibility and magnetization of the quark condensate on the external fields. The last part of the talk is dedicated to the examination of the Gross-Ooguri phase transition in the Wilson loop correlator in the presence of the gluon condensate.

03.04.2013 Irina Aref'eva (Steklov Mathematical Institute) "Quark-Gluon Plasma
Formation in Heavy Ion Collisions in Holographic Description" pdf
Abstract:
Starting from the discovery of QGP in heavy ions collisions at RICH,
a lot of theoretical efforts were applied to describe this phenomena within
QCD frameworks. The main problem is that this phenomena is dynamical and
in same time essentially nonperturbative. AdS/CFT correspondence,
which appeared as a
formal duality between the $N=4$ super Yang--Mills theory and
quantum gravity in the AdS background, has become a powerful tool
for studying various properties of real physical systems in the
strong-coupling limit.
The appearance of the quark-gluon plasma after the
heavy-ion collision in dual terms is described as formation of a
black hole. We discuss two holographic dual models of
thermalization.
In the first one colliding ions are described by gravitational shock
waves in AdS and the formation of the black hole is provided of
the formation of a trapped surface. In the dual language, the
multiplicity of the ion collision process is estimated as the area
of the trapped surface.
The second holographic model for quark-gluon plasma formed in the
heavy ion collisions is based on AdS-Vaidya model.
Within this model we estimate the thermalization time and its dependence on centricity
as well as
dethermalization time, related with the freeze-out time.

13.03.2013
Mikhail Zubkov (ITEP) "Nambu sum rule in the NJL models: from superfluidity to top quark condensation" ppt
Abstract:
It may appear that the recently found resonance at 125 GeV is not the only
Higgs boson. We point out the possibility that the Higgs bosons appear in
models of top-quark condensation, where the masses of the bosonic
excitations are related to the top quark mass by the sum rule similar to the
Nambu sum rule of the NJL models. This rule was originally considered by
Nambu for superfluid $^3$He-B and for the BCS model of superconductivity. It
relates the two masses of bosonic excitations existing in each channel of
Cooper pairing to the fermion mass. An example of the Nambu partners is
provided by the amplitude and the phase modes in the BCS model describing
Cooper pairing in the s-wave channel. This sum rule suggests the existence
of the Nambu partners for the 125 GeV Higgs boson. Their masses can be
predicted by the Nambu sum rule under certain circumstances. For example, if
there are only two states in the given channel, the mass of the Nambu
partner is $\sim$ 325 GeV. They together satisfy the Nambu sum rule $M_1^2 +
M_2^2 = 4 M_t^2$, where $M_t \sim $174 GeV is the mass of the top quark. If
there are two doubly degenerated states, then the second mass is $\sim$ 210
GeV. In this case the Nambu sum rule is $2 M_1^2 + 2 M_2^2 = 4 M_t^2$. In
addition, the properties of the Higgs modes in superfluid $^3$He-A, where
the symmetry breaking is similar to that of the Standard Model of particle
physics, suggest the existence of two electrically charged Higgs particles
with masses around 245 GeV, which together also obey the Nambu sum rule
$M_+^2 + M_-^2 = 4 M_t^2$.
Based on the papers:
arXiv:1302.2360 by G.E.Volovik, M.A.Zubkov,
and
arXiv:1301.6971 by M.A.Zubkov.

20.02.2013
Yu. B. Ivanov (Kurchatov Institute, Moscow) "Heavy-Ion Collisions within Multi-Fluid Simulations: Scenarios with and without Deconfinement Transition" pdf
Abstract:
Simulations of relativistic heavy-ion collisions within the three-fluid
model, employing a purely hadronic EoS and two versions of EoS
involving the deconfinement transition, are presented. The latter are
an EoS with a first-order phase transition and another with a smooth
crossover transition.
The analysis is performed in a wide range of incident energies
2.7 GeV $\le \sqrt{s_{NN}}\le$ 39 GeV in terms of the center-of-mass
energy. First results of these different scenarios are compared with
available experimental data. Scenarios with a deconfinement transition
look preferable at high incident energies $\sqrt{s_{NN}}\ge$ 5 GeV.
It is found that the predictions within deconfinement-transition scenarios
exhibit a ``peak-dip-peak-dip'' irregularity (in the dependence on the
incident energy) of the form of the net-proton rapidity distributions
in central collisions. This irregularity signals the onset of deconfinement
occurring in the hot and dense stage of the nuclear collision.

06.02.2013
Yuri Kalinovsky (LIT JINR) "Pion dissociation and Levinson's theorem in hot PNJL quark matter" pdf
Abstract:
Pion dissociation by the Mott effect in quark plasma is
described within the generalized Beth-Uhlenbeck approach
on the basis of the PNJL model which allows for a unified
description of bound, resonant and scattering states.
As a first approximation, we utilize the Breit-Wigner
ansatz for the spectral function and clarify its relation
to the complex mass pole solution of the pion
Bethe-Salpeter equation.
Application of the Levinson theorem proves that describing
the pion Mott dissociation solely by means of spectral
broadening of the pion bound state beyond $T_{\rm Mott}$
leaves out a significant aspect.
Thus we acknowledge the importance of the continuum of
scattering states and show its role for the thermodynamics
of pion dissociation.
Reference: arXiv:1212.5245

23.01.2013
Pavel Levashov (Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow) "Thermodynamic and transport properties of strongly-coupled degenerate electron-ion plasma by first-principle approaches" pdfppt
Abstract:
An approach is assumed to be a first-principle if it doesn’t rely upon any empirical information except for fundamental physical constants. This definition covers a great number of physical models, however, not all of them gives reliable results in the case of strong interaction and degeneracy. In this presentation several methods of calculation of thermodynamic and transport properties of strongly coupled quantum plasma will be covered: path-integral Monte Carlo, Wigner dynamics, density functional theory and quantum molecular dynamics. The advantages and disadvantages of these approaches will be considered and practical examples of computations will be mentioned. In particular, the methods will be applied to electron-hole plasma of semiconductors, hydrogen and deuterium as well as to dense plasma of metals. Comparison with available experimental data will be analyzed and further perspectives of first-principle approaches for strongly-coupled plasma will be discussed.

16.01.2013
Aleksander Gorsky (ITEP) "Nonperturbative defects in the dense QCD" pdf
Abstract:
We consider two types of nonperturbative defects
in the CFL phase of the dense QCD.
It will be argued that there are nonabelian strings
with a nontrivial worldsheet theory and monopoles
localized on the string worldsheet.

15.01.2013
M. Müller-Preussker (Humboldt University Berlin) "Confinement viewed with dimeron and dyon ensembles." pdf
Abstract:
We describe two recent attempts to simulate dimeron and dyon ensembles.
For zero temperature, following old confinement ideas put forward by Callan,
Dashen and Gross, (anti-) dimeron configurations are Monte-Carlo sampled
according to their classical action. We show that with an increasing bare
coupling the dimerons become more and more dissociating pointing to a meron
picture of the QCD vacuum state. Confinement is then viewed numerically in
terms of an area law of Wilson loops or an approximate linearly rising potential.
For non-zero temperature, guided by caloron solutions with non-trivial holonomy
as invented by Kraan and van Baal a couple of years ago, we discuss ensembles of
(anti-) dyon caloron constituents. Approximating them as Abelian monopoles one
analytically can compute the string tension as a function of the dyon gas density
and the temperature. On the other hand, simulating the monopole gas numerically
one easily sees that the long-range tails of their respective fields cannot be
simply treated within a finite volume. We describe that a solution of the severe
finite-size problem can be found with Ewald's summation technique well-known in
plasma physics. The numerical result obtained in the infinite volume limit nicely
agrees with the analytical result.
References:
1) F. Bruckmann, S. Dinter, E.-M. Ilgenfritz, B. Maier, M. Muller- Preussker, M. Wagner,
"Confining dyon gas with finite-volume effects under control", Phys. Rev. D85 (2012) 034502,
arXiv:1111.3158 [hep-ph].
2) F. Zimmermann, H. Forkel, M. Muller-Preussker,
"Vacuum structure and string tension in Yang-Mills dimeron ensembles", Phys.Rev. D86 (2012) 094005,
arXiv:1202.4381 [hep-ph].

11.01.2013
Florian Burger (Humboldt University Berlin) "Critical temperature and equation of state from $N_f$ = 2 twisted mass
lattice QCD" pdf
Abstract:
I will present results of our ongoing investigation of the finite
temperature QCD phase transition with
two flavors of maximally twisted mass Wilson quarks.
The determination of Tc from several observables is discussed and
the question of the universality class of the two-flavor theory will be
addressed by looking at the scaling towards the chiral limit and the
magnetic equation of state.
Further, I will present results for the trace anomaly, pressure and energy
density.

12.12.2012
Tin Sulejmanpasic (University of Regensburg) "Dyons in QCD and Chiral Symmetry Breaking" pdf
Abstract:
SU(N) calorons with nontrivial holonomy are a natural generalization of
instantons at finite temperature, which split into N objects called dyons.
As still in their infancy, a proper model of the vacuum structure
in terms of dyons is important to
develop. I will discuss some of
the implications of dyons and the
effect on chiral symmetry breaking for fundamental, as well as adjoint
fermions. Crucial objects for chiral symmetry breaking are fermionic
zeromodes on top of the dyons. In particular, the analytic behavior of
these modes is different for fundamental and adjoint fermions
and will induce a different behavior for adjoint and fundamental chiral
condensation, which
can potentially explain the different behavior in fundamental and adjoint
chiral transition observed on the lattice.

28.11.2012 Boris Kerbikov (ITEP) "Quark-antiquark system in ultra-intense magnetic field" pdf
Abstract:
We study the relativistic quark-antiquark system embedded in
magnetic field (MF). The Hamiltonian contains confinement,color
Coulomb and spin-spin interactions. We analytically follow the
evolution of the spectrum as a function of MF. In the large Nc
limit the mass of the ground state becomes negative for MF
above the critical value. The results are compared with recent
lattice calculations.

19.09.2012
Anton Kononenko (JINR) "Magnetic scenario of Quark Gluon Plasma. New lattice results in QCD and SU(3) gluodynamics"
Abstract:
New results of our ongoing lattice study aiming to support the magnetic
scenario of the quark-gluon plasma (QGP) will be presented.
To be concise, the magnetic scenario provides arguments that magnetic
degrees of freedom are responsible for the QGP's liquid properties.
On a lattice, these degrees of freedom can be associated with magnetic
monopoles obtained in the Maximal Abelian Gauge.
I will present numerical results obtained in lattice SU(3) gluodynamics
on one hand and lattice QCD on the other.
I will cover such topics as:
monopole density; dependence of the magnetic coupling and the magnetic
mass on the temperature. I will also consider several characteristics of
the monopole clusters in the confinement phase aiming
at better understanding of the quantum fluctuations responsible for
confinement in SU(3) gluodynamics and QCD.

27.07.2012
Michael Buballa (Technische Universitaet Darmstadt, Institut fuer Kernphysik) "Inhomogeneous phases in the QCD phase diagram" pdf
Abstract:
Most studies of the QCD phase diagram tacitly assume that the
different phases are homogeneous in space. However, there are good
arguments that inhomogeneous phases could also be present. In this talk we
focus on inhomogeneous chirally symmetry breaking phases,
where the quark condensate varies in space. Model calculations suggest
that the first-order chiral phase transition, including the critical
endpoint, could be removed from the phase diagram when inhomogeneous
phases are included. The mechanisms which lead to these solutions are
discussed and physical interpretations are given. Inhomogeneous color
superconducting phases are briefly discussed as well.

18.07.2012
V. G. Bornyakov (IHEP and ITEP) "Color-magnetic monopoles in lattice QCD at finite temperature: Most recent results" pdf
Abstract:
Thermal monopoles have been found to be important field configurations in
gluodynamics describing the gluon plasma close to the transition. We
present here results of a first study of thermal monopoles in
non-quenched lattice QCD with two flavors of dynamical quarks to
describe the quark-gluon plasma.
The density of monopoles and the parameters of their interaction are
computed both at high temperature and near to the transition.
A comparison with the thermal monopoles observed in gluodynamics is made.
References:arXiv:1111.0169 (by V. G. Bornyakov and A. G. Kononenko),
see also:
arXiv:1110.6308 and
arXiv:1104.1063

13.06.2012
Andrey Sadofyev (ITEP) "Chiral effects in superfluid" pdf
Abstract:
Recently, there were intense studies of hydrodynamics of chiral liquids.
A crucial novel point is existence of new transport coefficients,
overlooked in the text-book approaches. The coefficients are considered
to be completely fixed by the coefficient in front of the chiral anomaly.
This result could be obtained in a lot of approaches. Despite of variety
of the assumptions tried, all these approaches treat the liquid as a
single-component. We will consider here the system where the
single-component assumption is not valid and discuss which physical
picture is more justified.

06.06.2012
A. Leonidov (Lebedev Institute of Physics, RAS, Moscow) "Turbulent nonabelian matter in high energy nuclear collisions" pdf
Abstract:
Dense non-abelian matter created in ultrarelativistic heavy ion collisions
undergoes several stages of evolution, from initially produced glasma
through quark-gluon plasma to formation of final hadrons. In the recent
years there accumulated significant theoretical evidence for the presence
of instabilities and resulting stochastic tubulent-like state of glasma
and quark-gluon plasma. In the talk a review of these issues is given.

05.06.2012
Sunyoung Shin (BLTP JINR) "A dual geometry of the hadron in dense matter
by Bum-Hoon Lee, Chanyong Park, Sang-Jin Sin
published in JHEP 0907 (2009) 087 " pdf
Abstract:
This article discusses the dual geometries of confinement/deconfinement in
the hard wall model. Thermal charged AdS, which is the zero mass limit of
the Reissner-Nordstrom AdS black hole, is proposed as the dual geometry
corresponding to confining phase of QCD. We briefly review gauge/gravity
duality, hard wall model and Hawking-Page transition, and go through the
article. Below find the abstract of the article JHEP 0907 (2009) 087 :
We identify the dual geometry of the hadron phase of dense nuclear matter
and investigate the confinement/deconfinement phase transition. We suggest
that the low temperature phase of the RN black hole with the full
backreaction of the bulk gauge field is described by the zero mass limit of
the RN black hole with hard wall. We calculated the density dependence of
critical temperature and found that the phase diagram closes. We also study
the density dependence of the $\rho$ meson mass.

30.05.2012
V.V. Braguta (ITEP) "Electromagnetic superconductivity of vacuum induced by strong magnetic field: numerical evidence in lattice gauge theory" pdf
Abstract:
Using numerical simulations of SU(2) gauge theory we demonstrate that an external magnetic field leads to spontaneous generation of quark condensates with quantum numbers of electrically charged $\rho$ mesons if the strength of the magnetic field exceeds the critical value $e B_c = 0.927(77) GeV^2$ or $B_c =(1.56 \pm 0.13)* 10^16 Tesla$. The condensation of the charged $\rho$ mesons in strong magnetic field is a key feature of the magnetic-field-induced electromagnetic superconductivity of the vacuum.

18.05.2012
D. Blaschke (BLTP JINR and University Wroclaw, Poland) "A Microscopic Approach to Chemical Freeze-out in Heavy-Ion Collisions" pdf
Abstract:
The derivation of a formula for the chiral condensate in a hadron
resonance gas is presented. A model for chemical freeze-out is
presented where the melting of the chiral condensate in hot, dense
hadronic matter leads to an increase in the hadronic radii
facilitating fast chemical equilibration. The model predictions are in
agreement with recent results from the beam energy scan program
of the STAR experiment at RHIC Brookhaven.

2.05.2012
M.Tokarev (LHEP JINR) "z-Scaling & The Search for Signatures of a Phase Transition
and a Critical Point in Heavy Ion Collisions" pdf
Abstract:
The method of data analysis (z-scaling approach)
based on self-similarity and locality
of constituent interactions in hadron and nucleus collisions
at high energy is briefly described.
It is applied for the analysis of BES data in order to search
for signatures of a phase transition and a Critical Point.
Some results of the analysis of inclusive hadron spectra measured
in heavy ion collisions at RHIC over a wide range of the energies
√s_NN = 7.7-200 GeV are presented.
The microscopic scenario of constituent interactions in the framework
of this approach is discussed. The dependence of the energy loss on
the momentum of the produced hadron, the energy and centrality of the
collision is studied. The self-similarity of the constituent interactions
in terms of momentum fractions is used to characterize the nuclear medium
by a particular ``specific heat'' and the colliding nuclei by fractal
dimensions. Kinematical regions which are assumed to be the most preferable ones
to search for signatures of a phase transition of nuclear matter are discussed.
The discontinuity of the ``specific heat'' is assumed to be a signature
of crossing a phase transition or passing the Critical Point.

25.04.2012
B. V. Martemyanov (ITEP) "Topological objects across the phase transition
as seen by the cooling method
in SU(3) gluodynamics and in QCD with two flavors"
Abstract:
Topological objects are studied using the cooling method
of lattice fields representing SU(3) gluodynamics on one hand
and Quantum Chromodynamics with N_f=2 quark flavors on the other.
We compare the probabilities to find topological non-trivial,
in particular selfdual and antiselfdual configurations in the
cooling histories of Monte Carlo lattice configurations, that
have been generated close to the transition region in the two
phases, confinement and deconfinement.
In SU(3) gluodynamics (N_f=0) this probability drops sharply at
the temperature of the first order phase transition, while the
analytic crossover of full QCD from confinement to deconfinement
is accompanied by a smooth decrease of this probability.
The topological susceptibilities obtained by this analysis behave
in a similar way. The temperature behaviour of the latter is compared
with and found to be close to the temperature behaviour of the
topological susceptibilities determined by other methods.

18.04.2012
V. S. Filinov (Joint Institute for High Temperatures of RAS, Moscow) "Quantum Simulation
of Thermodynamic and Transport Properties
of the Quark-Gluon Plasma" pdf
Abstract:
For quantum simulations of thermodynamic and transport properties
of the quark-gluon plasma (QGP) within a unified approach we combine
Path Integral and Wigner (phase space) formulations of quantum mechanics.
Thermodynamic properties of a strongly coupled QGP of constituent
quasiparticles are studied by means of color path integral Monte-Carlo
simulations (CPIMC). For the purpose of simulations we have presented
the QGP partition function in the form of a color path integral with a
new relativistic measure instead of the usual Gaussian one used in
Feynman and Wiener path integrals. For the integration over the color
degree of freedom we have developed a sampling procedure according to
the SU(3) Haar measure. It is shown that this method is able to reproduce
the available Lattice Quantum Chromodynamics (LQCD) data describing the
deconfined phase.
Canonically averaged two-time quantum operator correlation functions and
related kinetic coefficients have been calculated according to Kubo formulae.
In our approach, CPIMC is used not only for the calculation of thermodynamic
functions, but also to provide equilibrium initial conditions (i.e. specific
coordinates, momenta, spin, flavor and color of multi-quasiparticle
configurations) in order to accomplish the generation of color-phase-space
trajectories as solutions of dynamic differential equations.
Correlation functions and kinetic coefficients are calculated as averages
of suitable Weyl's symbols of dynamic operators along these trajectories.
Using this approach we have calculated the diffusion coefficient and the
shear viscosity in good agreement with experimental data obtained at RHIC.
These results are obtained in collaboration with Yu. B. Ivanov (Kurchatov Institute Moscow and GSI Darmstadt, Germany), M. Bonitz (University Kiel, Germany), V. E. Fortov and
P. R. Levashov (both JIHT, RAS, Moscow).

11.04.2012
M.Tokarev (LHEP JINR) "Beam Energy Scan at RHIC &
Search for Signatures of Phase Transition
and Critical Point in z-scaling approach" pdf
Abstract:
The Beam Energy Scan program in AuAu collisions performed at RHIC is reviewed. The main goal of the program is the search for clear signatures of phase transition of nuclear matter and the location of a possible Critical Point. Experimental data on particle (π,K,p,φ,Λ,Ξ,Ω,…) and antiparticle yields allow to study collective phenomena as a direct and elliptic flow, nuclear modification factors, transverse momentum spectra, fluctuations of transverse momentum, particle ratios, net-baryon number and correlations of different quantities (Δφ-Δη) and their dependence on energy and centrality collisions. Results (temperature, chemical potential,..) of data analysis in framework of some theoretical models are discussed.
Method of data analysis (z-scaling approach) based on self-similarity and locality of constituent interactions in hadron and nucleus collisions at high energy is described. It is applied for analysis of BES data for search for signatures of phase transition and Critical Point. Some results of analysis of inclusive hadron spectra measured in heavy ion collisions at RHIC over a wide range of the energy √sNN = 7.7-200 GeV are presented. Microscopic scenario of constituent interactions in the framework of this approach is discussed. Dependence of the energy loss on the momentum of the produced hadron, energy and centrality of the collision is studied. Self-similarity of the constituent interactions in terms of momentum fractions is used to characterize the nuclear medium by a "specific heat" and the colliding nuclei by fractal dimensions. Kinematical regions which is assumed to be of most preferable for search for signatures of phase transition of nuclear matter produced in HIC in BES are discussed. Discontinuity of a "specific heat" is assumed to be a signature of phase transition and a Critical Point.

21.03.2012
O. V. Rogachevsky (VBLHEP JINR) "Event structure of multiparticle production in nucleus-nucleus collisions" pdf
Abstract:
The configurations of multiparticle events observed in the nucleus-nucleus
collisions are considered in the transverse momentum phase space. The
appearance of some features in the inclusive particle spectra may be
traced back to the different event structures. Event structure also
could have an impact on the some effects (flow, jet suppression, ridge),
observed recently in nucleus-nucleus collisions at RHIC and LHC.

11.03.2012
Nikolai Kochelev (BLTP JINR) "The Quark Anomalous Chromomagnetic Moment Induced by the QCD Vacuum,
a New Model for Pomeron and Odderon,
and the Nonperturbative Quark Energy Loss in Quark-Gluon Matter"
Abstract:
It is shown that the existence of strong vacuum gluon
fields called instantons in nonperturbative QCD vacuum leads to
appearance of a large anomalous quark chromomagnetic moment
(AQCM). We suggest a new model for Pomeron and Odderon exchanges based
on the AQCM and discuss the dynamics of exclusive high
energy hadron-hadron scattering at large momentum transfer. We
show that there is the nonfactorizable contribution to the
inclusive cross section for hadron production at high energy which gives
also the rise to single-spin asymmetries for meson
production observed in the many reactions. The possible important role of
AQCM contribution to the fast parton energy loss in cold
and hot quark-gluon matter is under discussion.

29.02.2012
J. Pawlowski (University of Heidelberg) "On the thermodynamics and phase structure of QCD" pdf
Abstract:
I review the progress made in recent years with functional continuum
methods in our understanding of the QCD phase diagram. Within this
approach QCD correlation functions of quarks, gluon and hadrons are
computed non-perturbatively from first principles. The approach has been
used complementary as well as in combination with lattice
computations, a particular strength being its applicability to the chiral
limit and at finite density. In the past decades this has led to a
plethora of quantitative as well as qualitative results for the hadronic
mass spectrum, the confinement-deconfinement and the chiral phase
transition, the role of fluctuations (non-Gaussianities) and the dynamics
of QCD far from equilibrium.
In the present talk I will mainly concentrate on the phase structure of
QCD at vanishing and finite temperature and density, including the effects
of strong (chromo-) magnetic and electric fields such as
present in heavy ion collisions. Specifically results are discussed for
the order parameters of confinement-deconfinement and chiral phase
transitions, the nature of these transitions and their interrelation, as
well as the thermodynamics of QCD. The talk concludes with a
discussion of the further prospects for our understanding of the phase
structure of QCD.

15.02.2012
A.G. Litvinenko (LHEP JINR) "Review of some results of heavy ion collisions. Continuation." ppt
Abstract:
In the second part of the talk, experimental results are discussed that
contain more specific information about the properties of the excited
hadronic matter. In particular, some properties of the elliptic flow
(scaling in the number of valence quarks, the elliptic flows of heavy quarks)
are presented. Besides this, the effect of melting of resonances and other
effects and observables, associated with the very early stage of the collision
between heavy ions, are pointed out. This concerns the effect of jet quenching
and the direct photon spectra.

01.02.2012
A.G. Litvinenko (LHEP JINR) "Review of some results of heavy ion collisions" ppt
Abstract:
Observables and basic definitions used to describe nucleus-nucleus collisions are discussed. The main results obtained at RHIC are considered in the review. Where it is possible a comparison with results obtained at other energies is made.

18.01.2012
Michael Mueller-Preussker (Humboldt-University Berlin) "Two-colour lattice QCD at T>0 in the presence of a strong
magnetic field"pdf
Abstract:
We present a lattice calculation for hadronic or quark-gluon
matter at non-zero temperature under the influence of a strong
magnetic field. We restrict ourselves to SU(2) gauge fields and
four degenerate dynamical quark flavours each having the same
electric charge.
We employ the staggered formulation for the fermionic lattice
fields and compute numerically the Polyakov loop and the chiral
condensate as well as their susceptibilities in order to establish the
dependence of the critical temperature on the external magnetic field. In
detail we discuss the enhancement of chiral symmetry
breaking in the chirally broken phase as well as its restoration
in the deconfined phase.

7.12.2011
Leonard Fister (University Heidelberg, Germany) "Yang-Mills Theory at Non-Vanishing Temperature"pdf
Abstract:
We study the temperature dependence of correlators in Yang-Mills
theory. For this purpose we utilise a purely thermal renormalisation
group flow equation, and obtain the full thermal propagators.
Interestingly, the electric screening mass is sensitive to the
confinement-deconfinement phase transition. We also compute
thermodynamic quantities such as the pressure.

16.11.2011
P.V. Buividovich (ITEP)"Nonrelativistic and Relativistic Hydrodynamics on the Lattice"
Abstract:
Lattice discretization of kinetic Boltzmann equation is one of
efficient ways for numerical simulations in viscous nonrelativistic
hydrodynamics,
which allows to consider turbulence, convection and other
non-equilibrium processes. We consider the derivation of macroscopic
hydrodynamical equations from continuum Boltzmann equation and from its
lattice discretization. It turns out that numerical solution of Boltzmann
equation on the lattice is simpler than the solution of the corresponding
Navier-Stokes equation. We also consider the
generalization of this approach to relativistic theory, in particular, to
the simulations of quark-gluon plasma.